1. Technical Field
This application relates to surface electromagnetic wave dispersive delay lines. It relates especially to high bandwidth dispersive delay lines formed in a compact spiral form factor.
2. Background Information
Dispersive delay lines have been used in defense technology for fifty years, first as matched filters for high power chirp radars, and then as an analog element in a Chirp Fourier Transform which is equivalent to an analog Fast Fourier Transform. By a simple factoring of the expression for the Fourier transform it can be shown that a temporal function or signal which is multiplied by a chirp waveform and fed into a dispersive delay line, matched to the multiplying chirp, produces a temporal waveform which is equivalent to the Fourier transform of the input time signal.
These properties allow signal processing of ultra wide band signals, which require upwards of 100 trillion operations per second, to be implemented without a large amount of massively parallel processing elements consuming tremendous electrical power. It is estimated that a cubic foot worth of surface electromagnetic wave dispersive delay lines and associated hardware consuming 10 watts would match the largest supercomputers at 1000 trillion operations per second in applications such as pattern recognition or neuromorphic computing.
Straight linear surface electromagnetic wave dispersive delay lines have been used since the late 1980s. See, for example, U.S. Pat. No. 4,808,950 to Apostolos et al. entitled “Electromagnetic Dispersive Delay Line”, issued Feb. 28, 1989.